I'm about to buy a 24-70 to fill a hole between my 12-24 and 70-200. I'm shooting DX (D90) but plan to upgrade to FX next year when the D700 refresh comes out. I also prefer the idea of a 24-70 length over a 18-55 f2.8 for the types of photos I shoot. I looked at a mailorder website to consider the alternatives. I recently got the 70-200 f2.8 VR2 and am very happy I chose the Nikkor glass. The main application for the 70-200 was sports and I really needed the best possible AF speed. I've heard the alternatives aren't as fast and any advantage here is worth the $$$. For a 24-70, my main application would be people and events. I've been using a 50 f1.8 AF and a 28 f2.8 AF, but I want a zoom so I do not have to change lenses and I insist on f2.8 because I want narrow d-o-f. In theory, the non-Nikkor options should be ok because people photography is not as AF-speed critical as sports... I looked on the mailorder website and I saw the following options (lots of alphabet soup)... Nikkor 24-70 f2.8 77mm G EDIF AF-S $1700 Tamron 17-50 f2.8 67mm SP XR Di-II LD aspherical IF AF-D $459 Tamron 28-75 f2.8 67mm SP XR DiLD-IF AF BIM $449 Sigma 24-70 f2.8 82mm EX aspherical DG DF AF $569 Sigma 17-50 f2.8 77mm EX DC OS HSM AF $669 Sigma 24-70 f2.8 82mm EX aspherical IF EX DG HSM $899 I'm willing to pay the extra $$$ (lots in this case) for the Nikkor glass if I have to, (I am very happy with the Nikkor 70-200 f2.8 VR2.) but it sure is a lot of $$$. I would think a 24-70 would be less critical than a 70-200. The downside of non-Nikkor glass might be sharpness, build quality, sample variation, and AF speed. AF speed is a big deal for a 70-200, but maybe not such a big deal for a 24-70. Looking at the online retailers website, every one of the alternatives has several reviews and nearly all of them cite disadvantages in build quality/sample variation and AF speed. Interestingly some of the negative comments about AF speed claim the alternatives are not fast enough for wedding use. They claim the lens hunts. I'm surprised by this. "Wedding" should be much easier than sports. If these lenses are not quite good enough for wedding, maybe I should just spend the $$$ and go for the Nikkor. Not to mention, most of the alternatives are not 77mm filters, so I would have to buy filters for them that would not fit my 70-200, 12-24, or future FX wide-angle zoom. Maybe that's not a big deal; after all I would probably only use filters on the standard zoom any way. I bought real Nikkor glass back in 1993 -- 300 f4 and 105 f2.8 micro -- and am very happy with the purchase. What do people think about these Sigma and Tamron alternatives? btw, I visited Yodobashi and BIC camera stores in Shinjuku earlier this week. We get better pricing in the USA for nearly everything.